On diseases the Clans faced and what they might actually be.
So I'm currently rereading TNP, and I came across a rather peculiar line in the book referencing an illness I've never heard before nor since to my memory. Blackcough.
To quote: "...weakened by hunger, the Clan would be in danger of greencough and deadly blackcough even more than usual."
Except, to my memory, Blackcough has never been mentioned before in any of the books. It doesn't come up in the first series, and so I'm left scratching my head about this one. I haven't read the books in some time until now, but if memory serves, these are the only diseases mentioned in any of the books, and for the heck of it, my theories on what they actually are.
Whitecough - likely a bronchitis of some sort
Greencough - more than likely pneumonia
The unnamed plague that ravaged ShadowClan and killed Nightstar - This is without a shadow of doubt a reference to the bubonic plague and it actually turns out that cats are very vulnerable to it, which is sorta ironic.
Poison - The illness that killed several Windclan cats during TNP. This is just straight up poison but I'll add it here anyways. Also as an aside, I'm not 100% sure, but I'm fairly certain that this isn't the same thing that forced Mousefur to retire to the Elder's den. It's similar, but it doesn't seem Mousefur was in mortal danger, iirc.
But now we have Blackcough, which to my knowledge no cat in the books is reported to have contracted, but from this single line of text we can assume it is probably one of the most consistently deadly illnesses that the Clans face... So what is it? My best guess is that it is feline tuberculosis. The name Blackcough hints at it clearly being a respiratory disease, and considering the emphasis that the book puts on a disease we've never heard of before in the series, it is clearly significantly worse than greencough, which we've already established is most likely pneumonia. But inadvertently, the book may have actually confirmed this as true by accident. As stated, this disease never comes up in any book prior to Moonrise. Now, while this could just be the Erins upping the stakes to show how screwed the forest is by this point, it also could hint at this disease being so rare that it's not seen often. And indeed, Feline Tuberculosis irl is incredibly rare to see, and it is difficult to treat, requiring intensive care and powerful antibiotics to treat to have even a chance of a cat pulling through. So in Clanlife, this disease would be almost guaranteed to be fatal most cases, which could potentially explain why it's called Blackcough, because it's an illness that is simply just associated with death to most medicine cats. To an extent that could also explain why it's not mentioned prior to this book; because it's a disease no cat wants to risk having to encounter in their lifetime, so it's best to not say it often.
With that said, that is just a theory. I don't know if the Erins have ever actually openly explained or shed much light on the illnesses of the Clans, but I saw Blackcough mentioned and I got hung up on it. Thanks for reading this theory!